<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
<style type="text/css">
        .bounce {
    position: relative;
}
.bounce > div {
    width: 40px;
    height: 40px;
    background: #1ab394;

    opacity: 0.6;
    border-radius: 50%;

    position: absolute;
    top: 0;
    left: 0;

    animation: bounce 8s infinite ease-in-out;
}

.bounce > div:nth-child(2) {
    animation-delay: -1s;
}

@keyframes bounce {
    0%, 100% {
        transform: scale(0);
    }
    50% {
        transform: scale(1);
    }

}
</style>
</head>
<body>
<div class="bounce">
    <div></div>
    <div></div>
</div>
</body>
</html>